| dc.description.abstracteng | Despite potentially diverging interests, members of social groups coordinate to maintain group cohesion. The mechanisms and processes of group coordination are modulated by species- and context-specific factors. The genus Papio (baboons) has been proven to be a good model for the investigations of group coordination processes. It comprises six closely related species, which live in different habitats and social systems. Since baboons are adapted to a largely terrestrial life and occur in habitats similar to those where our hominin ancestors evolved, group coordination processes in baboons might be also a model for group coordination in our ancestors, when language was not yet at hand. In particular the multilevel social organization of baboons potentially offers parallelisms with group coordination patterns in the multilevel human society.
My project aimed to cover the missing knowledge about the patterns of group coordination in wild Guinea baboons and discuss results in a comparative perspective. Guinea baboons live in a multilevel society, with high socio-spatial tolerance and no linear dominance hierarchy among males. The basal level of the society is the reproductive unit, which consists of one adult male (“primary male”) with one or more affiliated adult females. Several units aggregate in a party, which includes also adult males without affiliated females (“non-primary male”). Two or three parties form a gang. I focused on the coordination process during group departures from a stationary state and while the group is “on the move”, during group travel pro¬gressions. Specifically, the first goal was to explore who influences timing and direction of group departures. Research on other baboon species, living in various social systems, revealed a preeminent but not exclusive role of adult males during group departures, irrespective of the social system. Therefore, Guinea baboon adult males were expected initiating group departures and succeeding more than females as found in other baboon species. Alternatively, because of the relative tolerant nature of this species, both sexes might have a more equal influence on the coordination process compared to other baboon species. The second goal was to understand whether the presence of two levels of social organization in the group (unit and party) affects the coordination process in departures and progressions. In the multilevel system of Guinea baboons, individuals may need to balance the interest of maintaining spatial cohesion with members of their subgroup with overall group movement of larger social entities. Therefore, members of the same unit were expected to move cohesively within the party both during group departures and group progressions. The third goal was to describe the order of group members during travel progressions. Studies on group progressions of travelling baboons generally conveyed that adult males take position mainly at the front and, to a lesser extent, the rear of the travelling group, while females and juveniles occupy more often central positions. This order has been interpreted as an adaptation to predation risk, with the most risky positions at group edges. Given a similar predation pressure for Guinea baboons, they were expected to show a similar pattern of progression order as other baboon species.
Research results show that young baboons almost never attempted an initiation of group departure and adult males attempt initiations of group departures more often than adult females. This suggests that adult males have a higher influence on the decision outcome, but that adult females can still have an impact. Interval times of dyads of individuals belonging to the same unit were significantly shorter than the interval times between individuals not belonging to the same unit, both during group departures and group progressions. This means that individuals aim to keep proximity firstly with their unit members and secondly with the other party members. During group progressions, adult male Guinea baboons tend to travel occupying front positions, whereas middle positions are taken more often by adult females and young individuals. Positions at the rear of the group were equally taken by individuals of all age/sex classes. Primary males, in contrast to non-primary males, tended to keep position closer to the centre where their females and offspring were. Non-primary males travelled more frequently at the edges of travelling groups.
Taken together, these findings conform to a general consistency across baboon species in the group coordination processes, despite different social and ecological contexts. As a result, the basic mechanisms underlying coordination processes emerged already in the baboon common ancestor, or even earlier in primate history. Major determinants of the processes of group coordination appear to be social dominance, feeding opportunities, predation pressure and body features (e.g., body dimension and weight, canines).
My study, as others, revealed several theoretical and empirical issues when analysing group coordination in wild animals. One problem concerns the complexities of potentially influencing factors on group coordination during collective movements. To resolve this problem, I suggest to (i) conduct comparable studies on related species to better point out the effect of few potentially influencing factors; (ii) conduct experiments to control the effect of potential influencing factors on the coordination process (e.g., modifying food access); (iii) strengthen automated data collections of small scale movements (e.g., remote sensing, GPS); (iv) simulate group coordination during collective movement (e.g., agent-based modelling); (v) include anecdotal observations. Another problem regards some assumptions at the basis of most hypotheses and discussions about group coordination during collective movements in primates. Precisely, group movements are assumed to involve firm individual interests across events. These individual interests are driven by the individual fitness and set selection pressure on the system. However, this assumption of firm individual interests may not be always justifiable. In many situations different forms of group coordination could lead to the same impact on individual fitness, i.e. the basic requirements of group members will be satisfied, irrespective of the processes of group coordination. Ideally, it is required a distinction between group coordination processes under conditions of markedly divergent individual interests to those not under such conditions. I suggest a distinction between group departures from the sleeping site and other group departures during the whole day as a first step toward this purpose. | de |